Pen needle assemblies are known in the prior art for use with pen injectors. Pen needle assemblies are individually provided for a pen injector and include a hub attached to a needle. Typically, the assemblies are formed to be removably mounted to the pen injector and disposed after use. With multiple-dose pen injectors, a plurality of pen needle assemblies are mounted and removed from the injector.
The needles used with pen needle assemblies are of limited length. The needles must have sufficient proximal length to pierce a septum of a medicament reservoir and have sufficient distal length to be inserted into a patient for a medical injection. Prior art pen assembly designs have been found to cause “tenting” of a drug reservoir septum when the proximal part of the needle does not sufficiently pass through the septum. As such, the septum may not be fully penetrated or the septum is distorted resulting in possible incorrect drug administration. An overly-sized proximal portion of the needle may be used to avoid “tenting.” However, an excessively long needle in the proximal direction may not efficiently convey medicament from low levels in a drug reservoir.
Additionally, pen needle assemblies are typically attached to the pen injector by rotating the needle, while inserting the needle into the septum of a medicament reservoir. The combined rotating and traversing motion of the needle may cause coring of the septum. The septum is formed to be resealable upon removable of the pen needle assembly. With a cored septum, a portion of the septum may not be resealable, resulting in the need to dispose of the reservoir.